Self-cleaning strainer



2, 1954 R. v. SEAHOLM SELF-CLEANING STRAINER 4 Sheets-Sheet 1 Filed March 3, 1950 & Q1

INVEN TOR. mgofzi fea/whz, BY W/ZQZMMMW 1954 R. v. SEAHOLM SELF-CLEANING STRAINER 4 Sheets-Sheet 2 Filed March 3, 1950 Feb. 2, 1954 R. v. SEAHOLM 2,667,975

SELF-CLEANING STRAINER (Q IN VEN TOR.

Patented Feb. 2, 1954 OFFICE...

SELF-CLEANING STKAINER Rudolph-V. Seaholm, ChlcagmllL ApplicationMalch" 3," 1950, *S erial No;147 ,460 16 Claims- (01. 210152') The present invention: pertains-to improve= ments in a self-cleaning strainer adapted to -filter sediment, impurities or r foreign matter-and the like from liquids, which strainer is of high capac-* ity, considering its compact size, and 'is well adapted for large scale mining, industrial or' municipal installations.

The strainer is of the type illustrated-and described in my prior copending applicati'omSerial'No. 17,755, filed March 29, 1948, now- Patent No. 2,626,710, dated January 27, 1953; andtheinvention deals with various structural improve ments in the latter for the purpose of obtainingincreased liquid= handling capacity, improvedreliability, decreased cost of manufacture, 'faoilitated inspectionand maintenance andimproved operating characteristics in general.

It isan object of the present invention to" pro vide an'improved self-cleaning liquid strainer ofthe foregoing type, whether a multi-stage instal lation employing a plurality of individual m'ov able screens spaced longitudinally of the direction of flow of the liquid to be strained, as illustrated herein, or a single-stage'type, in" which strainer I a screen or screens of improved construction-'areemployed, presenting a maximum effective screening area for a given overallscreen'size? Specifically, an object 'of the invention is to provide a strainer which includes one or more im= proved; reciprocatory type straining screens,

characterized by a-rectangular frame aipluralityof cross ribs extending across the fr ame which are spaced from one another in the direction of i reciprocation thereof and are alternately overlapped relative to one another in the dir'ectionof liquid flow through the screen, i. e., transverse of" the direction of reciprocation, and a flexible; mesh-type straining screen element sustained al--' ternately at the overlapped ends of the successive ribs in a fashion to produce a longitudinally cor-' rugated screening surface which presents maxi-- mum eflective screening area for a given area of the frame on which the screen is supported Another object of the invention is to pro-- vide a corrugated straining screen structure' of:

the foregoing type.

of the screening action by controlling the direc' manner.

A further object of the invention is' toprovidef' a strainer includinga housing: having inlet and genera'r way of' the nature of the inventioni but- 2 discharge passages,- a screen structure' 'including a rigid screenor staged screens movable in 'said 1 housing transversely 'of -the direction or path-' offiow between said passages, and screen back- 1 wash means of an improved, simplifiedcharacter disposed in-receiving relation to the screen or sc'reensfin -which:said-backwash means take theform' 'of a 'p'ai r of wastechannels dispos'edbn opeposite' sides of the liquid "flow path and Ii crossed :i

by the "screen 'structurein" the movement there-l of, and in which the screen embodies imperfor'atew blocking 1 elements reciprocable therewith and disposed on opposite si'oles' of the screening area thereof to :block "said: waste channels 'alternately..-' "as the screen moves 'thereacross, .therebyi in:- swing against the discharge through said waste channels of liquid other-than thatwhich has performed .the "screen backwashing function.

It 'is' an object to providea strainer having a movable screen and improved screen backwash ing provisions of-the sort referred to-in-the precedingparagraphtogether with means to control the desired rate of backwa'shing. in l a very simple and convenient manner.

Anotheriobject'is to provide an improved screen includingapervious' fluid straining area. prefer= ably characterizedbysa flexible 'mesh' element"- and alternately overlappe'd'supporting ribs there-' for; as described above; in combination with. one or' more imperforate blocking elements reciprocable withthe screen in fixed, laterally'adjacent" relation to :saidperviousarea for the purpose" refe'rredto above.

A still further object or the invention is to pro-= vide a strainer; illustratively .embodied as a re'-" ciprocable scree'n," self-cleaning type; including means to move the strainer F screen transversely" of' -astrainer housing "aorossthe path of "liquid flowing through the 1 housing and an -indi'ca'tor elementse'curedto the screen-and visible-from'theexterior of "the housingfor the purpose of "enabling an'observer to'determine the rate of-move ment ofthe'screem Yet another and more specifie objectis to pro 'vide a strainer "construction including Ta scr'een,

means to reciprocate the "screen transverselys'of a strainer housing and anindicating element 'se-' cured to -the screen and projecting' externally 10f the housing for the purpose re'ferred to in the preceding paragraph; in -'which said screen is operatively'connected to the reciprocatingmean's and; to i the indicating element Y in an 1 improved fashion;

The foregoing 'state'me'nts are indica'tive in a will be appreciated that the invention is susceptible of incorporation in other modified forms coming equally within the scope of the appended claims.

In the drawings,

Figs. 1 and 1A are co-related views in end elevation illustrating, respectively, the exterior of the housing of a two stage strainer installation and the hydraulic screen actuating cylinder of the unit, together with the hydraulic power and control provisions which are operatively connected to the latter, the method of effecting the connection being indicated in broken lines;

Fig. 2 is a somewhat enlarged view in horizontal section through the strainer of Fig. 1, approximately along line 2-2 of that figure, showing the relationship of the staged screen, screen backwash and screen operating provisions of the illustrated unit;

Fig. 3 is a view in side elevation of the strainer unit ofFig. 1, being partially broken away in section in a vertical longitudinal plane approximately along line 3-3 of Figs. 1 and 2, further illustrating the relationship of reciprocatory screens to the respective housing guides and backwash channels associated therewith;

Fig. 4 is a view in transverse vertical section along a broken line generally corresponding to line 4-4 of Fig. 3, further showing the screen and reciprocating mechanism for the latter, being partially broken away to more clearly indicate the backwash channel liquid inlet and provisions opening to the interior of the strainer housing;

Fig. 5 is an enlarged plan view, partially broken away, generally illustrating the dual reciprocating screen which is employed in the illustrated strainer;

Fig. 6 is a greatly enlarged fragmentary view further illustrating the screen construction, being in horizontal section on a line corresponding to line 6-6 of Fig. 3; and

Fig. 7 is a fragmentary view in elevation, further illustrating details of the improved screen construction, being viewed from a plane coincident with the lower margin of Fig. 6.

Referring particularly to Figs. 1 and 1A of the drawings, the strainer unit is generally designated by the reference numeral l0, being characterized by its pronounced compactness notwithstanding a large liquid handling capacity. A hydraulic power and control unit H is operatively connected with strainer unit ID by means of the hydraulic pressure conduits l2, l3, preferably of a known armored flexible type, leading to the power mechanism M of the unit ID. This mechanism is a double acting, reciprocating plunger and cylinder type which requires no further description than to state that it embodies a plunger which reciprocates in a cylinder under the control of the unit II, its plunger being directly connected to the reciprocating screen of the unit [0, to be described.

The strainer unit'comprises a hollow cast or forged housing I5 of generally rectangular shape, made up of the central flanged body members or castings 16, two of which are clamped together toconstitute the main body of the boxlike strainer housing 15, and the coactingfianged stituted by a pair of heavy braced metal plates 'and a timer unit 32.

Waste liquid employed in the backwashing of the screen of the strainer is discharged from the bottom-of the housing [5 through a discharge line 2| which is controlled by a manual valve 22-. Liquid to be strained enters the housing through a flanged inlet fitting 23 having a circular inlet passage 24 opening to a vertically elongated inlet throat 24', as illustrated in Figs. 2,, 3 and 4. The strained liquid exits from the housing through the vertically elongated discharge throat 25 and circular discharge passage 25' of a discharge fitting 26 located on the opposite side of the housing from the inlet fitting 23 and in alignment with the latter.

The hydraulic power and' control unit ll shown in Fig. 1A comprises a suitable supporting framework 28 providing cross supports 28 for a hydraulic liquid supply tank 29, a positive displacement pressure pump 30, a four-way, solenoid-controlled valve 3! of'standard type Unit 32 is electrically connected to the valve 3| to govern the energization of the solenoid element of the latter. It does this in properly timed fashion to control the application of hydraulic pressure through valve 3| to produce the desired reciprocation of the strainer screen. It has not been deemed necessary to illustrate specific details of these timer and solenoid valve mechanisms, nor the electrical operating connections thereof, in view of the conventional character of these devices and the further fact that the manner of interconnecting the same will be apparent to one skilled in the art and understanding the operation of the strainer unit [0. It is the sole purpose of the timer 32 and solenoid valve 3| to f periodically reverse, at equal intervals, the supply and exhausting of hydraulic liquid through the conduits l2, l3 at opposite ends of hydraulic cylinder Id.

The tank 29 contains a supply of the hydraulic pressure liquid, which is preferably a suitable grade of hydrocarbon lubricating oil of relatively low viscosity, in order to minimize the possibility of freezing at low temperatures. However, it is contemplated that, if desired, the water or other liquid strained by the system may be employed as the pressur liquid. The liquid is withdrawn from tank 29 to the intake of the pump 39 through a supply pipe '33 and is discharged at the pump outlet 34. The latter in turn discharges to a conmechanism l4 through one or the other of conduits I2, l3 in an obvious manner.

Relief valve 35 is a conventional, springbiased piston type having the function of returning to th'etank'2 9, through an over-capacity return line 1 asses-'28 31, the exc'e'ss of *the pressure--1iquidover andabove-that which" is requiredfor'*the operation of the hydr aulic-power mechanisrn- I45 Anappro v priate-adiustable *needltype throttling unit "38 fdr the purpose or controlling the speed'of recip rocat-ion of the plunger ofmechanism ld by-contr'olling therate of-supply and exhaust of-hy draulic' liquid through-conduits 12, l3.- Alternatively,-or-"as a supplement to the -function"of-unit** 38, the conduits I2, [3 may be providedwithrnan- Liquid returned toso1enoidvalve 3! from-"the hydr'aulic" power mechanism l4 *through one or thothr "of the conduits *1 2, l 3, as determined by timer 32', is' forwarded to tankfiSthiough areturn line -3 92 It has been found desirable to ern-' ployth'e special tank construction illustrated in Fig$1Ato-cool the returning hydraulic liquid: In-

order to improve the heat transfer quality 'of the tank; the latter is provided with horizontal and vertical air tubes 29' extending thereacross'and opening-to the top bottom and sides-thereoffbeing; of course, in properly sealedrelation to these tank members. Moreover, it is desirable toprovide thereturn lines 3'! and 39 to the tank with" flareddischarge provisions above the normal liquid level in the tank 29 "by Whichthe'returning oil issprayed and cooled as it enters th tank.

Such means is typified by the flared dischargewall 'of the casting .is similarly shaped at H.

wardly of the'enlargement il andthevertically elongated discharge throat 25 of the housing,'the

recess being-coextensive in height withthe throat andopening to the latter;

A reciprocatory screen, generally designated 48,

is guided insets of parallel, upper andlower ways or guide tracks 51],51 and"'52,' 53,- respectively;

whichare formed in the central housingsection' I65" Thescreen 48 comprises a transverselyex'- tendingcrosshead 54 which is provided at either end thereof with a pair of parallel; inner and outer,apertured, screen frame members 55; 55; respectively,of flat, generally; planar, plate-like construction. Said members are spaced laterally in parallel relationto one another by anintermediate rectangular planar frame 57, in 'afmanner' to definea rectangular screen openingefii The width of this opening exceeds somewhat the spacing-of the opposite sides of the respective wastechannels 45 "from'one another.

A "braced mesh screen structure, generallyides-' ignated 59, is mounted in opening 58 "tostrain" liquid impinging the screen' fro'm the intake throat 24 as thescreen d B is-reciprocated acrossthe housing. Details of construction and aoescription of the advantages of this particular screen structure Will be hereinafter set forth;

On the opposite sides of the screenopening 58 the :frarne members 455,- Mare provided with ex tensions .intthe :form of the fiat rectangular, im=

perforate,-'blocking elements omplateswi' These zsingthescreen' w torou 1?forreciprocation by" are 'ofi-isuch -size and" are sir-spaced "from one an-- other that duringthe--time thatthe screen"ispassing and beingba'ckwashed through one "of the eback'wash channels 45, as f indicated by -arrowsin Fig52,-'theother backwash channel, on

theopposite side of-intake throat-24"; is blocked by anelement 60-5 This insures-that 'in'nocase will liquid"other*=than that which has been backwash'ed be discharged intoeither of the channels #5: Loss or operating efficiency of the --installationis accordingly insured against.

The present unit *features a dual screenconstructibn, in "which" the primary and secondary screens"are-generallydesignated 62 and63, re-' However, it is "to be understood that theforegoing principles are equally" applicable to a "single-stage strainer andfofcoursejto a-strainer having more thantwo spectivel'y; todistinguish the same.

stages:

' Bashwashing results simply fromthe' reverse" flow of liquid through the screen" into the backwash'channelflli under the pressure inthe housing' as the 'screen is progressively exposed to the channels 45 inreciprocating across the latter.

Further-backwash provisions onthe downstream side 'of' theprimary screen'fiz are not required,"the pressurewithin' the housing being adequate" to causethe desired backwash flow.

Backwashing of the secondary screen'63 is like wiseacc'omplished solely by the :liquid pressure existing inrecess 41 onthe downstream side of saidscreen; the dischargeand backwash fiowat' this pointbeing representediby' the small ar rows. the ,secondaryiscreen 63 are indicatedby" the reference numeralfi'abeing inthe formof vertically' elongated grooves in the cast backwash" members" 66 which'are disposed immediately adjacent the upstream side of said secondary screenp Thesemembers BBmay be integral with the housing section H5, or may be separate members which are appropriately pinned thereto. The primary and secondary screen backwash channels 45;65; respectively, discharge through the'respective passages 6?, 68 in section 56 to the well or-sump-B inthe bottomof the housing from which the waste liquid is withdrawn through the 'waste fitting. tothe'valve controlledwaste line 2! leading to an appropriatedisposal point. The manuallycom trolled'valve 22in the last named line may be em played "to control the rate of flow therein, there-- bycontr'ollingithedesired rate of backwashing, whichwillvaryin different installations.

Theinvention includes an improved arrange ment', shown in Fig.2, for connecting the screen 48 tothe plunger ofthehydraulic unitM, in order to enable the entire screen assembly to be withdrawnfrom" the housing without removing the "hydraulic'unit; To this end, an elongated screen actuating rod 13 is removably connected to thepiston rod 15 of theplunger unit (shown as extendingjthr'ough' the end plate N3 of the housinglby a threaded connection 16; Th -rod" .13 is provided with a shoulder abutting the screen frame-cfosshead-54*at- 17, the rod being reduced in diameter adjacent the shoulder and extend ing-through' 'a bore 18 in said crosshead.

'A-further'frod which is used as an" indicating element carries anenlarged end filwhich abuts the oppositesi'deof the crosshead 5 and is.re-

movably 'sec'uredto the extremity of actuating rod 73 by .means of the threaded connection 8f. According1y,the indicator rod '1 9' servesin clamp- The backwash channels associated; with This fitting connects the-hydraulic unit l4 and is correspondingly re- 7 ciprocated by the same connection.

gland or packing 82 in the end wall of the extension IQ of the housing end plate l1, being visible from the exterior of the housing. Thus it is possible to observe the travel of the rod I9 for a check on the rate of reciprocation of the screen structure. The end plate extension I9 receives the screen crosshead 54 in its reciprocation, as indicated by dotted lines in Fig. 2.

When it is desired to remove the screen from the housing, the end plate H is removed, whereupon the indicating element 19 is unscrewed to release the screen from the connecting rod 13, following Which the screen may be readily withdrawn outwardly. If desired, the connecting rod 13 may be threadedly released from the plunger rod 15 in a similar fashion, although thi is ordinarily not necessary.

The screen structure 59 of the strainer is of improved character, in its specific details, as shown in magnified scale in Fig, 6, leading to increased economy of production, greater ruggedness and resistance to damage and wear, and greater efiiciency of action. The structure includes a plurality of relatively thin but stiff, plate-like ribs 84 which extend vertically across the frame opening 58 at a right angle to the direction of cross reciprocation. They are of substantial width, in the direction of the thickness of the screen frame, being in the illustrated and preferred embodiment of a width greater than one-half of said thickness but less than the full thickness of the frame. Alternate ribs have their outer side margins substantially flush with the opposite surfaces or sides of the frame, hence they necessarily overlap one another at their inner extremities in the lateral sense. Said rib are enlarged at their inner side margins and are spaced across the frame in the direction of its reciprocation, in the alternately overlapped or staggered fashion shown in Fig. 6. Accordingly, when the flexible mesh screen 85 of desired fineness is threaded or reeved about the overlapped inner side margins of the ribs 84, a, zigzag corrugated screen outline results. This afiords a maximum effective straining area for a given cross-sectional area of opening 58. It is evident that in constructions of the foregoing type it is possible to produce practically any effective screening area desired, greatly in excess of that presented by an ordinary fiat screen surface. Ribs 8G on the respective halves of the screen are transversely braced and rigidified by the spaced, parallel, horizontal webs 84 formed integral with the ribs. The webs 84 present inner faces of V- shaped outline which engag against and support the screen 85 against distortion. The opposite edges of the ribs 84 lie flush with the outer edges of the ribs, so as to present a coplanar outer surface of ribs and webs. This affords a very desirable sliding bearing for the reciproeating screen in its movement past th backwash channels.

In order to insure proper passage ofthe liquid through the screen 85, I propose to undercut the ribs rearwardly of the enlarged and rounded outer extremities 85' thereof, as by hollow fillets 86. Accordingly, liquid flowing parallel to ribs 84 is caused to flow through the screen 85 in a direction approximating th normal to its surface.

A further advantage of the above described screen construction arises from the fact that considerable space between the screen, and forwardly of the oppositely extending rib on the downstream side, is available for the reception of relatively large objects such as fish, pieces of bark or wood, etc. These objects 7 are caught in the space referred to and discharged through the backwash channel as the screen reaches and passes across the same, without causing any tendency to damage the screen the opposite side of the throat is kept closed 7 by the blocking element 60. These elements act as valves to control the amount of backwash, thereby insuring against waste of liquid other than the backwash liquid. One-half of the screen is active at all times as a strainer during the time that the other half is being backwashed and none of the screen is idle or dead at any time. The amount of backwash water is controllable for any given installation by manipulation of the manual valve 22 in discharge line 2!.

The action at the secondary screen 63, of which the element is relatively fine in mesh, is similar to that described above, both as to the straining and backwashing features, and, having passed said secondary screen, the liquid discharges through the throat 25 of discharge fitting 26.

Control of the rate of reciprocation of the screens may be had by throttling at the main control valve element 38, or by individual speed control valves l2, #3 for the purpose of synchronizing the speed of the plunger of hydraulic unit H3 and the timer setting. The speed of reciprocation is ascertained by inspecting the externally projecting indicator rod (9.

The foregoing strainer construction is very simple, compact and inexpensive in its parts but highly efficient in operation. It is possible to wash both screens 62, 63 up to sixty times per;- minute, as distinguished from existing commercial strainers in which screen washing is performed only three to six times per minute. The

improved screen can handle liquids having 25% i essary to replace the flexible mesh element 85 thereof.

I am aware that those skilled in the art will perceive the possibility of various modifications or alterations of the foregoing strainer without departing from the principle of the invention. I therefore desire that the appended claims be construed to cover all such obvious refinements.

I claim:

1. In a straining apparatus, a housing having intake and discharge passages and means defining a path of liquid fiow therebetween, a

screen guided for movement in said housing transversely of said path of flow of liquid, backwash means in .said housing including waste any given pair of similarly extending ribs 84 on the upstream side of 79 echannelst-disposed downsstream-i.ofgssaid screen thereto,.and imperforate blockingelements fixed ,landionv-thel-side thereofatowardlsaid intake ,pastoeithensideof said. straining .unit which are .sage,-;said channelsnbeingl spaced if-romoneuanspaced fromone-another in accordance with the other on opposite ,sidesof said path of vflow, .said Y. spacing -ofssaid wastechannelsand are moved channelssopeningato the housing v interiorqinv re- 5 periodically ,into .blocking alignment with the Hceiving relation .to liquid .flowing reversely latter, and .meanscto reciprocate said screen through the screen, said screen comprising ,a .across.saidibackwashmeans to bring said strain- .generallyplanarliquid-perviousstraining unit of wing. unitnand eblockingrelements in successive predetermined tareagmountedain sliding.,,engage- -\alignment with said. backwash channels, said ment .with .thehinterior .of.. said housing; to pass xil0,.blocking,.elementsweach being..oi...a size. to cover across theopeningof.saidswastechannels .therethe. respective channels and-interrupt backwash to and .imperforate, (blocking elements. .fixed to ,l theretowhen sol aligned therewith.

..eitherside of said. strainingunitwhichare, spaced .weiaIn. va. straining. apparatus, a housing havfrom one. anothertiniaccordancewith .thespacingintakeandldischarge passages and means deins f aid waste channels. and iareflmoved .pe-.=: fining a path ..or; liquid flow .therebetween, a riodically into blocking alignment ,withwthe lat- .-screen guided. for -,movement V-in said.housing ,ter andameans. to-.move..said-sc-reen relative/to transversel'yioisaid path ofiflow of liquid, plural saidbackwashimeans tobring saidstr ningunit backwash-.meansinsaid housing. spaced from one di i k ns 1 r1 r1 s ir1 uc e sive alignment another on, oppositevsidesof saidpath ofiflow uwithsaidbackwashchannels, saidblocking 618-020 in receiving relation to 1iquid flowing through men hl e a fr z to c v rli h r p ,.the.screen saidiscreen .comprisingia generally .tive channels .andinterrupt l. backwash thereto planar,.liquid;pervious straining ,uniti of..predewhen so. aligned. therewith. termined -,area,.mounted, in a. sliding engagement Q -II arsv i n .app il n ollsinglhavmg with theinterior of.said housing to .passvacross in ak d discharge p ages; and means .defin- 7.25 theopeningeoflsaid iwastetvchannels. thereto, and ing .a pathioi liquidwfiow.therebetween,ascreen imperforate .,blocking elements .fixed toeither u ded for mov m in d housing transversely .side .ofsaid-straining ,unit' whicheare. spaced from "of .saidnpa fi fl WO quid, backwash means one another, inwaccordancelwith. the spacing of .iinisaidf housin -ri l m wa te c ls .dissaid waste channels and arelmoved periodically poseddownstream of. said screenandon the side into blocking alignment "with the, latter, and thereof" ds s ni passage, said chanmeans to move said screen relative to. saidbackin'elsibeing spaced from. one .anotherhon oppowashimeansi .tocbring said straininglunit and "sited-Sides of. said .vpaiih 1 f fl said Channels sblockingwelementsninsuccessive alignment with ,opening toithehousing' interior in receiving. relasaid backwash ;,means, said .blocking elements tion to .liquid flowing reversely through :thex hbeing of. a, size tovcover the respective chanscreen, said screenicomprising. asgenerally planar .nels vand. interrupt ,c backwashythereto when. so ZQliquid-pervious straining "unit of vpredetermined aligned-therewith.

a eanm u tedl inslidin engagement with the Samoa/straining apparatus lauhousing. having interior ,of-saidhousing to pass.across.'the openintake.and.dischargeipassagesland meansdefin- ,ing of said waste. channels thereto,,.said unit beiO ing a path of l iquid fiow the eb tw n, a screen ing in the form ofia wire, meshmerhber, spaced guided forireciprocationin said housing transf mesm mbers al rn ly engaging pposite lversely-of.,said.path,of flow .of 1iquid,i, meansto sides .of said members .andsimperforateblocking reciprocate said screen, andbackwashi means .in elements-fixedtoeither sideot said strainingunit aid housing. including ..waste-,channels on the whichnarespaced frommone another in accords downstreamsideofsaidscreenwhichare spaced w.ance hwithithemspacing of said "waste channels fromuoneianojther linithehdirection loft reciprocaa d are m v d periodically into l king .aiign- .itionefathe screen andare in receiving relation .ment with theielatteni. and lmeans; to. move said tomliquid flowing. reversely through .thescreen, screen relative. tosaid'backwashmeans .tobring said screen comprisingiaisupporting. frame prosaidsmesh straining member ..and-blocking 'elevided..with.- a,pervious straining member and immen s in Suc e s e alignment. i h s dlbac perforatelblocking,elementsion.either sideof said washhchann'els, saidelementsbeingwof sufiicient straining lmemberwhichuare spaced from one .size tdblo'ck onel-of the. channels to. said reverse vanother .in-V accordancewith the spacing of said .ba'ckwash'jflow while the. other channel is exposed .wastechannels to, block one thereofto said rethereto, and vice versa, said ,blo'ckingzelements versebackwashjfiow.while the other channel is ,ea'chbeing of a size to. cover the respective chan exposed1;thereto, and vice versa, said blocking ,n'els' and interrupt backwash thereto when so elements eachlbeing of a size to cover the reali neditherewith. spective channels andinterrupt backwash there- :3; In a straining apparatus, a housinglhavto. when aligned therewith.

ing intake and'discharge passages and means 16.77In a liquidstraining apparatus characterdefining, a-path of liquid flow therebetween, a ized by a.housing having aligned intake and screen-guided for reciprocating movement inxsaid discharge passages and means defining a .path '.h'ousing;transversely of' said 'path of flow of .of liquid "flow .therebetween, a screen frame liquid, backwash means-insaid housing in'cludmounted: to :travel across said path of liquid ing'waste channels disposed'downstream of said flow,=said'frame;having a-tplurality ofilaterally screen'andon' the side thereof'towardsaidvinspaced, ribs extending thereacross, which ribs take'passage; said'channels' beingspacedJfrQm are disposed withpadjacent .ends in alternate, onepanother; on opposite sides of .said path of transversely.overlapped'relation to one another flow, saidchannels opening to the'housing intein said direction .clf'fiowand a flexible foramiriot in receiving relation to liquid "flowing renated screen'unitdisposedl'in zigzag outline about verselyj. throughlthe screen, said screencompristhe overlapped ends of said valternate ribs, and ringwa;generally planar.;liquidep ervious. straining .means. to .move. said frame. transversely i of. said vunit ofapredetermined: area mountedsins sliding pathiof fiow.-in .theldirectionoi the plane of. the engagcmentswithethe interior iofe, said. housing to frame. ipasse across the: opening? 10f; said .waste channels 15 '7 ,A liquidt. straining... apparatus ,cornprisingi a 1 games fir housing a generally planar screenframeimovably mounted in saidhousing, said frame having aplurality of laterally spaced parallelribs extending from side-to-side thereof, which ribs are disposed with adjacent side margins in alternate transversely overlapped relation to one another,

i a foraminated mesh screen carried by said frame,

said screen being disposed in zigzag outline about alternate overlapped margins of said ribs, said "ribs each presenting a convex forward portion in engagement with said screen and a concave side surface'connecting said convex portion to the remainder of the rib to direct flow parallelingthe latter through the screen at a substantial anglethereto, backwash means in said housing in sliding relation to said screen frame and in receiving relation to said screen, and means ,to move said frame transversely of said last named means in the direction of the plane of the frame.

' 8. A liquid straining apparatus comprising a housin a generally planar screen frame of predetermined thickness. movably mounted in said housing, saidframe having a plurality of laterally spaced parallel ribs extending from side-toside thereof, which ribs are of. less width than the thickness of said frame and are disposed with adjacent side margins in alternate transversely overlapped relation to one another, therespective alternate overlapped rib margins terminating in transversely spaced relation to the opposite surfaces of said frame, a foraminated mesh screencarried by said frame, said screen being disposed in zigzag outline about, alternate overlapped margins of said ribs,.said ribs each presenting a convex forward portion in engagement with saidscreen and a concave side surface connecting said convex portion to the remainder of the rib to, direct flow paralleling the latter through thescreen at a substantial angle thereto, backwash means in said housing in sliding relationto said screen frame and in receiving relation to said screen, and means to move said frame transversely of said last named means in the direction of the plane of the frame.

9. A liquid straining screen comprising a generally planar screen frame having a plurality of laterally spaced parallel ribs extending from side-to-side thereof, which ribs are disposed with adjacentside margins in alternate transversely overlapped relation to one another, and a foraminated mesh screen element carried by said frame, said screen element being disposed in zigzag outline aboutthe alternate overlapped margins of said ribs, said ribs each presenting a convex forward portion to engage said screen element and a concave side surface connecting said convex portion to the remainder of the rib to direct flow paralleling the latter through the screen element at a substantial angle thereto.

10. A liquid straining screen comprising a generally planar screen frame of predetermined thickness having a plurality of laterally spaced parallel ribs extending from side-to-side thereof,.which ribs are of less width than the thickness of said frame and are disposed with adjacent side margins in alternate transversely overlapped relation to one another, the respective alternate overlapped rib margins terminating in transversely spaced relation to the opposite sides of said frame, a foraminated mesh screen element carried by said frame, said screen element being disposed in zigzag outline about said alternate overlapped margins ,of said ribs, said ribs each presenting a convex forward portion to engage said screen element and a concave side surface connecting said convex portion to the remainder of the rib to direct flow paralleling the latter through the screen element at a substantial angle thereto, and an impervious blocking element of substantial area on said frame adjacent said screen element.

11. A liquid straining apparatus comprising a housing having intake and discharge passages and means defining a path of liquid flow therebetween, a generally planar screen frame mounted to travel across the path of liquid flow, means to move said screen across said path, said frame having a plurality of laterally spaced, slat-like ribs extending thereacross, which ribs are disposed with adjacent side margins in alternate, transversely overlapped relation to one another in said direction of flow, and having parallel, spaced wibs extending between said ribs to rigidify the same, and a flexible foraminated screen unit disposed in zigzag outline about the overlapped margins of said alternate ribs, said Webs and ribspresenting side margins substantially flush with the respective opposite side surfaces of said frame which have sliding and bearing engagement with an interior surface of said housing.

12. A liquid straining apparatus comprising a housing having intake and discharge passages and means defining a path of liquid flow therebetween, a generally planar screen frame mounted to travel across the path of liquid flow, means to move said screen across said path, saidframe having a plurality of laterally spaced, slat-like ribs extending thereacross, which ribs are disposed with adjacent side margins in alternate, transversely overlapped relation to one another in saiddirection of flow, and having parallel, spaced webs extending between said ribs to rigidify the same, and a flexible foraminated screen unit disposed in zigzag outline about the overlapped margins of said alternate ribs, said webs being shaped adjacent the opposite sides of said respective alternate ribs and said webs being substantially coplanar to present a fiat bearing surface for sliding engagement with the interior of said housing.

13. A liquid straining apparatus comprising a housing having intake and discharge passages and means defining a path of liquid flow therebetween, a generally planar screen frame mounted to travel across said path of liquid flow, said frame having a plurality of laterally spaced ribs extending thereacross, which ribs are disposed with adjacent side margins in alternate, transversely overlapped relation to one another in said direction of flow, and a flexible foraminated screen unit disposed in zigzag outline about the overlapped margins of said alternate ribs, backwash means in said housing in sliding relation to said screen frame and in receiving relation to said screen unit, a backwash blocking element carried by said screen frame to one side of said screen unit, and means to move said frame back and forth transversely of said path of flow.

14. A liquid straining apparatus comprising a housing having intake and discharge passages and means defining a path of liquid flow therebetween, a generally planar screen frame mounted to travel across said path of liquid flow, said frame having a plurality of laterally spaced ribs extending thereacross, which ribs are disposed screen unit disposed in zigag outline about the overlapped margins of said alternate ribs, backwash means in said housing in sliding relation to said screen frame and in receiving relation to said screen unit, said means including backwash channels in laterally spaced relation to one another on opposite sides of said intake passage and backwash blocking elements carried by said screen frame on opposite sides of said screen unit, and means to move said frame back and forth transversely of said path of flow.

15. As an article of manufacture for use in a liquid straining apparatus, a reciprocatory liquid straining and blocking screen comprising a generally planar frame having a plurality of laterally spaced parallel ribs extending from sideto-side thereof, which ribs are disposed with adjacent side margins in alternate transversely overlapped relation to one another, a foraminated mesh screen element carried by said frame, said screen element being disposed in zigzag outline about the alternate overlapped margins of said ribs, an impervious blocking element on said frame adjacent said screen element, said blocking element having an imperforate surface of substantial area in the plane of a side surface of said screen, said imperforate surface extending a substantial distance outwardly from an end of said screen side surface, and means on said frame to reciprocate the screen in the direction of the plane thereof.

16. As an article of manufacture for use in a liquid straining apparatus,a reciprocatory liquid straining and blocking screen comprising a generally planar frame of predetermined thickness having a plurality of laterally spaced par- 14 allel ribs extending from side-to-side thereof, which ribs are of less width than the thickness of said frame and are disposed with adjacent side margins in alternate transversely overlapped relation to one another, the respective alternate overlapped rib margins terminating in transversely spaced relation to the opposite surfaces of said frame, a foraminated mesh screen element carried by said frame, said screen element being disposed in zigzag outline about said alternate overlapped margins of said ribs, an impervious blocking element on said frame adjacent said screen element, said blocking element having an imperforate surface of substantial area in the plane of a side surface of said screen, said imperforate surface extending a substantial distance outwardly from an end of said screen side surface, and means on said frame to reciprocate the screen in the direction of the plane thereof.

RUDOLPH V. SEAI-IOLM.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,585,817 Bailey May 25, 1926 2,077,589 Seaver Apr. 20, 1937 2,184,177 Burrell Dec. 19, 1939 2,253,692 De Grave Aug. 26, 1941 2,310,587 McNeil Feb. 9, 1943 2,340,592 Holm et al Feb. 1, 1944 FOREIGN PATENTS Number Country Date 2,328 Great Britain 1858 

